Pellicles and process relating to same



Patented Feb. 1, 1938 UNITED STATES PATENT VFFICE Thomas F. Banigan, Kenmore, N. Y., assignor, by

mesne assignments, to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application December 18, 1935,

Serial No. 55,079

10 Claims.

This invention relates to the prevention of iron stains, and in particular, it pertains to the treatment of pellicles of non-fibrous character, such as those made from regenerated cellulose, which 5 are adapted for use as bottle caps, bands and the like, in order to prevent staining of the pellicles when dried in contact with iron or metals containing iron as a component.

Heretofore, when regenerated cellulose caps and bands in a gel condition, 1. e. after coagulation and regeneration but before being dried, were applied to bottles having iron-containing metallic caps or appurtenances, a common defect has been that the cellulose caps and bands 15 developed rust stains which appeared on the surface and greatly injured the appearance of the finished package. In addition, the portion stained with rustbecame weakened and tended to crack at these points.

Caps and bands of regenerated cellulose, which have been manufactured, for instance, by the viscose process, are customarily stored in the gel state, i. e. before they have been dried and while they still contain considerable water, and are taining glycerin or other softener. The consumer withdraws the cap or band from the shipping solution and applies it over the bottle or other desired'container or object and allows it to dry. In drying, it shrinks considerably and grips the object tightly. If, in so doing, the cap or band comes into contact with iron or metal containing iron, rust stains will 'develop, which impart an unsightly appearance and a destructive action to the cap or band. When the cap or band is opaque, as for example when it contains titanium oxide or other light-colored pigment as an opaquing agent, the unsightliness due to the iron stain is quite pronounced. 40 In my copending application, Serial No. 737,428, I have described a method of preventing stains on non-fibrous, cellulosic pellicles when in contact with iron-containing metals. Briefly, this method consists in shipping the pellicles in an aqueous solution containing a stain preventive agent. The stain preventive agents disclosed generally are those having an alkaline reaction in aqueous solution, such as trisodium phosphate and triethanolamine. These agents, however, 5 generally increase the tendency of the dyes in pellicles dyed with direct dyestuffs, to bleed or diffuse into the solution. This bleeding is a common difiiculty with pellicles dyed with direct dyestufis even when stain preventive agents are not included in the solution. Additionally, these shipped to consumers in an aqueous solution constain preventive agents are not compatible in solution with substances that prevent bleeding, for example alum, since it tends to precipitate therefrom aluminum hydroxide, aluminum phosphate or other aluminum salt and/or to destroy the rust preventive action of the preventive agent. Finally, trisodium phosphate, while a good iron stain preventing agent, brings out insoluble precipitates when hard water is used. Triethanolamine, on the other hand, is compatible with hard water but is not as good a stain preventing agent as trisodium phosphate and also is quite expensive.

It is an object of this invention to produce non-fibrous pellicles which resist staining when in contact with iron-containing metals.

It is a further object of this invention to prevent iron stains in caps and bands of non-fibrous sheet materials which are applied in a gel state to bottles or other containers having iron-containing metal caps or appurtenances, and which caps and bands attain their ultimate condition as the result of shrinkage through the loss of moisture.

It is a still further object of this invention to reduce the tendency of dyes in pellicles dyed with direct dyestuffs to bleed or diffuse into the solution in which said pellicles are placed.

Other objects of the invention will appear hereinafter.

The objects of this invention are accomplished,

in the preferred form, by shipping the covering material in an aqueous solution containing a .small amount of an alkali or alkaline earth nitrite, and especially sodium nitrite. For 0011- venience, the invention will be described in terms of the latter.

I have discovered that iron stains can be greatly diminished and even completely prevented by using gel cellulosic pellicles which have been treated with a solution of sodium nitrite in hard or soft water. I have discovered furthermore that in shipping such pelliclesin iron containers, the use of sodium nitrite reduces the tendency of the containers to rust and discolor the pellicles. Finally, I have made the remarkable discovery that instead of increasing the tendency of'the dyes in pellicles dyed with direct dyestufis to bleed or diffuse into the shipping solution, as is usual with other rust or stain preventingagents, this tendency to bleed is reduced.

In applying the principles of the invention, the gel pellicles are immersed in an aqueous solution containing sodium nitrite and the immersion is continued until equilibrium is established between the solution and the pellicles. It is customary to ship gel regenerated cellulose bottle caps and.

bands in a dilute aqueous glycerin solution, the glycerin acting as a softener. The caps and bands may be placed in the shipping container and the treating solution containing the desired amount of glycerin and sodium nitrite then poured in until it covers the pellicles, after which the container may be closed and shipped, and the treated caps and bands, whenever desired, placed on the bottles or like vessels, and permitted to dry and shrink over the tops of the bottles.

It is preferred that the treating solution also contain a preservative for the cellulose, for example, a preservative such as is' disclosed in Wright U. S. Patent No. 2,013,739, issued September 10, 1935.

As explained above, sodium nitrite and its equivalents can be used in hard water without causing undesirable precipitates. This, of course, is a great convenience when a supply of soft water is not available.

The following illustrative example describes a mode of applying the invention.

Example Gel caps and/or bands of regenerated cellulose prepared from viscose and adapted to be applied to bottle tops and necks, are dyed with a direct dye and the dyed gel pellicles are then packed in a shipping container containing a solution of glycerin and sodium nitrite in hard or soft water, in such a concentration that, after equilibrium with the moisture in the caps and/or bands is reached, the shipping solution contains about 5% of glycerin and about 0.1% of sodium nitrite. The solution may also contain a preservative such as chlorinated cresol.

Examples of direct dyes which may be used to dye the regenerated cellulose gel pellicles of the above example, are Pontamine Fast Scarlet 438 (Color Index 326), Pontamine Sky Blue 63X (Color Index 518), Pontamine Fast Yellow NNL (Color Index 814) and Erie Orange WS.

As equivalents of sodium nitrite in the practice of this invention may be mentioned the nitrites of other alkali metals and of alkaline earth metals, for example potassium nitrite, calcium nitrite, strontium nitrite.

Caps and bands treated in accordance with the above example, when dried down over iron or iron-containing metal bottle caps, even when the latter are filed down to expose the bare metal, remain completely free from rust stains even after a. long period of time.

The proportion of nitrite present in the equilibrium solution which is used to ship the pellicles may vary from a fraction of a percent up to the limit of solubility of the nitrite in the solution. For most practical purposes, the equilibrium solution will contain from 0.01% to 3% of said nitrite. It is preferably kept as low as possible in the interest of economy.

The invention, in its preferred form, applies to the treatment of regenerated cellulose pellicles obtained from viscose, but it may also be applied to regenerated cellulose pellicles obtained from cuprammonium cellulose solution, or to the treatment of cellulose esters such as cellulose acetate, or to cellulose ethers such as ethyl cellulose or glycol cellulose which have been cast in water solution, or to pellicles of gelatin, casein and related substances. The invention may be applied wherein any such pellicles come in contact with iron under conditions where ironsstaining might take place in a manner similar to that explained in connection with gel regenerated cellulose caps and bands.

While the invention is preferably applied to gel pellicles, it will be understood that the scope to the spirit of the invention is intended to be included within the scope of the claims.

I claim:

1. A non-fibrous, hollow gel pellicle which is subject to shrinking by loss of water and which is subject to staining when shrunk in contact with iron, said pellicle containing a water-soluble nitrite of a metal, taken from the class consisting of alkali and alkaline earth metals.

2. A non-fibrous, hollow cellulosic gel pellicle Whichis subject to shrinking by loss of water and which is subject to staining when shrunk in contact with iron, said pellicle containing a pigment and a water-soluble nitrite of a metal taken from the class consisting of alkali and alkaline earth metals.

3. 'A non-fibrous, hollow gel pellicle which is subject to shrinking by loss of water and which is subject to' staining when shrunk in contact with iron, said pellicle being dyed with a direct dye and containing a water-soluble nitrite of a metal taken from the class consisting of alkali and alkaline earth metals.

4. A hollow regenerated cellulose gel pellicle subject to shrinking by loss of water and subject to staining when shrunk in contact with iron,

said pellicle having been dyed with a direct dye and containing a light-colored pigment, being further characterized in that it also contains a water-soluble nitrite of a metal taken from the class consisting of alkali and alkaline earth metals.

5. A hollow regenerated cellulose gel pellicle subject to shrinking by loss of water and subject to staining when shrunk in contact with iron, said pellicle having been dyed with a direct dye and containing titanium oxide, being further characterized in that it contains sodium nitrite.

6. The process which comprises treating nonfibrous hollow gel pellicles subject to shrinkin by loss of water and subject to stainingwhen shrunk in contact with iron, with an aqueous solution containing a water-soluble-nitrite of a metal taken from the class consisting of alkali and alkaline earth metals.

7. The process which comprises treating a non-fibrous, hollow cellulosic gel pellicle containing a pigment and. being subject to shrinking by loss of water and to staining when shrunk in dyestufi, then treating said pellicle with an aqueous solution of a water-soluble nitrite of a metal taken from the class consisting of alkali and alkaline earth metals, said nitrite reducing the tendency of the dyestuff to bleed in said aqueous solution.

9. The process which comprises treating a hollow regenerated cellulose gel pellicle subject to shrinking by loss of water and to staining when shrunk in contact with iron, with a direct dyestuff, then treating the pellicle with an aqueous solution of a water-soluble nitrite of a metal taken from the class consisting of alkali and alkaline earth metals, said nitrite reducing the tendency of the dyestufl to bleed in said aqueous solution.

10. The process which comprises treating a. hollow regenerated cellulose gel pellicle containing titanium oxide and being subject to shrinking by loss of water and to staining when shrunk in contact with iron, with a direct dyestuil, then subjecting the dyed pellicle to an aqueous solution of sodium nitrite, said nitrite reducing the tendency of the dyestufl to bleed in said aqueous solution.

THOMAS F. BANIGAN. 

